Polyamides, commonly referred to as nylons, are known polymers having amide groups in the polymer backbone. Polyamides have achieved great commercial success as used in synthetic fibers and engineering resins, and if not too crystalline, as plastics.
Although polyamides have many desirable characteristics, modification of the properties of the polymer would be useful. For example, for certain applications, it would be advantageous if the polyamides would have reduced crystallization kinetics so as to produce amorphous materials or materials with low crystallinity. Additionally, in some applications, it would be advantageous to raise the glass transition temperature ("T.sub.g ") of polyamides (as defined hereinafter). Also, it would be advantageous to increase the hydrophobicity of polyamides.
One known method of altering the characteristics of the polyamides is by synthesizing discrete polyamide copolymers, also, substituents are often added to the nylon chain to reduce crystallinity. Both techniques, however, are very difficult and often expensive.
Blending polyamides with other classes of polymers is an option to copolymerization, however, it is not predictable whether the blend will be miscible or immiscible. A major feature encountered when two polymers are mixed is that in the majority of combinations, the blend is immiscible and components tend to phase-separate to form heterogeneous mixtures. Immiscible blends are not desirable because they have low physical attractive forces across phase boundaries and suffer from delamination at the phase boundaries. Consequently, immiscible blends have inferior properties when compared to the pure components and therefore are limited in their usefulness. Polymer blends that are miscible, on the other hand, are desirable because they are not phase separated. Miscible blends are one-phase compositions where the stratification of the polymeric components during or after processing is generally avoided, thus allowing the blend composition to be useful for many applications. A number of methods may be used to determine the miscibility of polymer blends, such as, for example, optical transparency (in the absence of crystallinity), a single glass transition temperature (T.sub.g), nuclear magnetic resonance, transmission electron microscopy, and excimer fluorescence (as discussed in Concise Encyclopedia of Science and Engineering, Ed. J. I. Kroschwitz, published by John Wiley & Sons, Inc., 1990, pp.629-632). As discussed herein, by miscible blends, it is meant that blends of two or more polymers behave as a single homogeneous material, exhibiting a single T.sub.g.
There is a continuing need to discover methods to increase the versatility of polyamides.